About Me

Australian philosopher, literary critic, legal scholar, and professional writer. Based in Newcastle, NSW. Author of FREEDOM OF RELIGION AND THE SECULAR STATE (2012), HUMANITY ENHANCED (2014), and THE MYSTERY OF MORAL AUTHORITY (2016).

Wednesday, August 04, 2010

Goodbye, Torosaurus?

Recent research published in the Journal of Vertebrate Paleontology by John Scannella and Jack Horner, from the Museum of the Rockies, suggests that Triceratops was actually a juvenile/young adult form of Torosaurus (or that Torosaurus was a more mature form of adult Triceratops).

As the animal aged, the shape of its bony frill and iconic collection of three horns altered, with the frill growing longer, holes developing in the frill's bonework, and the horns shifting downward and forward in orientation. Thus, no smaller and younger specimens with the distinctive Torosaurus appearance are ever found. Rather, the converging evidence is that the small number of Torosaurus fossils are actually from more mature specimens of Triceratops. Fossils of the more mature Triceratops specimens already classified as such can be seen taking on Torosaurus characteristics.

Though not stated explicitly in the New Scientist article, the name Torosaurus is the one to be abolished, as Triceratops (1889) is the older of the two names to be applied to the species. At this stage, it's not clear to me whether abolition of the name Torosaurus (1891) has obtained general acceptance among paleontologists - hence my question mark in the title of this post. Perhaps not, as these things take time, but it's pretty clear that specimens at the Museum of the Rockies, at least, will be reassigned as Triceratops.

More generally, this is just one example, albeit a dramatic one, of dinosaurs changing morphology with age. This can make it difficult to establish whether larger and smaller fossils of similar animals represent distinct species or older and younger specimens of the same species. Thus, Nanotyrannus is now widely believed to be a juvenile form of Tyrannosaurus rex, though this is disputed by some paleontologists and the issue is still not settled. Again, it is claimed Dracorex and Stygimoloch are immature specimens of Pachycephalosaurus.

4 comments:

I remember memorising all these names when i was a young lad. It was hard work, but i will be sad to see Torosaurus go nonetheless.On the other hand, it will be easier to teach them to my son now.A fascinating article indeed.